1. Field of the Invention
The present invention relates to a process for preparing a composition containing an alkenyl succinic anhydride. More particularly, the present invention relates to a process for preparing a composition containing an alkenyl succinic anhydride and having an excellent hue, from an olefin and maleic anhydride.
2. Description of the Prior Art
An alkenyl succinic anhydride has a wide range of applications in the fields of resin modifiers, plasticizers, dispersing agents, lubricating oil additives or rust-preventing agents. The alkenyl succinic anhydride can readily be prepared by subjecting an olefin and maleic anhydride to a thermal addition reaction at a high temperature of e.g. from 200.degree. to 220.degree. C. However, substantial amounts of unreacted maleic anhydride and olefin remain in the thermal addition reaction product, whereby a purification process is required. As a method of minimizing the unreacted materials, it has been proposed to prolong the reaction time. However, in such a method, a part of maleic anhydride is likely to undergo decomposition, and by-products are likely to form, whereby substantial coloring is likely to result, and the quality of the product will be impaired and the application of the product will be limited. Further, an additional purification process for the removal of the by-products will be required.
Maleic anhydride has a high melting point and is readily sublimated. Accordingly, during the removal of the unreacted materials by heating the above-mentioned reaction product under reduced pressure, the sublimated maleic anhydride is likely to deposit on the inner wall of the piping, whereby a trouble of clogging is likely to be led.
On the other hand, a compound obtained by copolymerizing an olefin and maleic anhydride in the presence of a radical-generating agent, is used in certain fields similar to the fields of application of the alkenyl succinic anhydride. This copolymerization reaction is conducted usually at a temperature of from 90.degree. to 200.degree. C. i.e. substantially lower than the temperature of the thermal addition reaction, whereby the resulting product has a good hue without coloring due to the formation of the by-products. Further, the conversion is generally good, and there is no substantial possibility of the trouble due to the sublimation of maleic anhydride during the removal of the unreacted materials by distillation. However, the compound obtained by this radical reaction is a high polymeric substance having a relatively high viscosity and a relatively high melting point, as compared with the alkenyl succinic anhydride. Accordingly, the compound does not provide the same level of effectiveness as the alkenyl succinic anhydride although it is used in the same fields of application as the alkenyl succinic anhydride.